Tuning fork generator



A. L. MATTE April 19, 1932.

TUNING FoRN GENERATOR Original Filed June 16, 1928 \S ALS J3 J@ R, W1

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INVENTQR @.jlze BY c ATTORNEY CII Patented Apr, 19, 1932Kiv UNITED STATES PATENT OFFICE ANDREW L. MATTE, OF SUMMIT, NEW JERSEY, ASSIGNOR T0 AMERICAN TELEPHONE AND TELEGRAPH COMPANY, A. CORPORATION 0F NEW YORK TUNING FORK GENERATOR Original application led June 16, 1928, Serial No.

286,042. Divided and` this application med Hay 15,

1930. Serial No. 452,641.

This invention relates to tuning iforks and tuning fork generators, and more partmular- .ly to arrangements for producing current of the frequency of vibration of a tuning for? or of some harmonic of its frequency of v1- bration.

This is a division of a copending application, Serial Number 286,042, tiled June i6, 1928.

In general, the vibration oi a tuning forli may be made to generate an alternating current in two distinct ways. First, the vibra--s tion of the tuning fork may be made to change' the reluctance'of a magnetic path or circuit to thereby generate an electromotive `force in a coil overwound on some portion of this magnetic path or circuit. Second, the hux ci a magnetic path or circuit may remain virtually constant, yet the fork may bey made to vibrate` so that the change in the position oi its tines or prongs may divert some of the ilux from a number of turns of the coil in which an electromo'tive force is to be generated. The

difference between these two methods will be readily apparent if one recalls that the electromotive force generated when a coil is threaded by a magnetic ield is dependent upon the rate of change of the linkages formed by the turns of the coil and the enclosed lines of magnetic induction. Thus, an electromotive force may be produced either by changing the amount of flux enclosed by a given number of turns of wire or by changing the number of turns ofwire enclosing a given number of lines of .magnetic induction. The principles underlying the two methods enumerated hereinabovewill be employed in connection with the invention to be subsequently described.

One of the primary objects of this invention is to generate an alternating current by the continuous action of a tuning fork, the tuning fork being electrically driven.

Another object of this invention is to prevent the electrical driving means of the tuning fork generating arrangement from aEectn ing or interfering with the generating action. While' this invention will be'pointed out with particularity in the appended claims, the invention itself, jects and features will be better understood from the detailed description hereinafter following when read in connection with the accompanying drawings, in which Figure l shows how the number of edective turns oi a coil of wire may be periodically changed; llig. 2 shows how the flux threading a coil of wire may be periodically changed; and lli g. 3 shows another embodiment or an electrically driven tuning fork generator for rendering the edect oi the driving ux substantially negligible in the circuit producing the generated current. Figs. l and 2 are included herein to show different types of electrically driven tuning :fork generators. Fig. 3 shows the tuning fork generator which is claimed as novel in this divisional tion. A

Referring to Fig. l of the drawings, there is shown a tuning fork F having two tines or prongs P1 and P2. The-tuning fork may be mounted very solidly on a rigid, heavy base which is supported on a soit, dili'used bed such as may be provided by pads of rubber. This fork may be made, preferably, of ordinary soft steel although it will be clear that it may be made of any well-known'alloy, particularly one which exhibits magnetic properties and which is easily maintained in mechanical vibration. y

A coil of wire W1 wound on a core of iron R1 is placed between the tines or prongs P1 and P2 a considerable distance from the free ends of these tines or prongs. The current that may iiow through the winding W1 is supplied by a local source of direct current such as is designated as B1. One terminal of the source B1 is connected to a contact D, while the other terminal of thisv source is connected tothe winding W1. When the conboth as to its further obo applicasurge through the windin g tact K is closed, current will ow from the source B1 through the winding W1 and over the curved portlon of the tuning fork F between contact K and the fixed contact D.

The tuning fork F mag be started by pulling the prongs P1 and 2 together, i. e., in-

wardly. After being started, it is driven continuously, the ener for 1ts continuous operation being suppli from the source B1.

The contact K provides a make-and-break circuit which periodically interrupts the direct current flowing from the source B1. Thus, after the prongs P1 and P2 have been drawn together, the contact K will be opened so that no current may iiow from the source B1 through the Winding W1. As these prongs. become released, soon the contact K will become closed and current will then flow from the source B1 through winding W1. Accordingly, that winding will become excited and its core will become threaded withA a dense magnetic field. 'The prongs P1 and P2 will then be attracted, thereby opening the circuit including the source B1 and the winding W1 at the contact K. Later, contact K will be closed and another pulse of current will V1 and the prongs P1 and P2 will be attracted, i. e., drawn ,inwardly again. And, so it continues.

Another core of magnetic material is laced adjacent to the free ends of the prongs P1 and P2, this core being so spaced from the free ends of these prongs that gaps J1 and J2, respectively, are established. A coil of wire W2 is wound about a portion of the core R2 adjacent to one of the prongs such as P1. Coil W2 has a plurality of turns of wire so spaced that the length of the coil in the direc- "of the winding W2 force of varying magnitu tion of its axis 1s about equal to, and no greater than, the corresponding dimension of the adjacent prong P1. The winding W2 is connected to an output circuit S.

As the tuning fork F vibrates, a magnetic field is intermittently established by winding W1, as has been explained hereinabove. A portion of its magnetic flux will flow through the rounded portion of the fork F (which is at the left of the winding W1). Another portion of this ma etic field will flow over the prongs P1 and 2 and over the iron bar or core R2. As the fork F vibrates, the magnetic field passing through the bar R2 will intermittently cut more or less of the turns of wire of coil W2. In other words, as the fork vibrates, the number of effective turns will `be continuously changed and, consequently, an electromotive de will be established across its terminals. Consequently, an alternating current may iow through the circuit S, the frequency of which will have a component equal to the frequency of vibration of the fork F. Even if the flux density through the core R2 were to remain substantially constant asthe fork F vibratesan alternating current would be produced by virtue of the change in the number of eective gurus of the coil of wire W2 threaded by that Fig 2 shows a different arran ement embodying some of the principles o this invention, `'n which the flux densit threading a coil of wire is varied While al of its turns remain in the path of lthe threading flux. In this arrangement, a core of iron R, is laced between the prongs P1 and P2 of the ork F so that gaps J 1 and J1 are respectively established between prongt P1 and P2 and the ends of the core R1. The driving circuit for maintaining the fork F in vibration after it is started is the same as has been described in connection with the arrangement of Fig. 1, similar reference characters designating similar parts. 4

As'the fork vibrates, the size of the gaps J 2 and J 2 are intermittently changed so that the reluctance of the magnetic circuit, which is threaded b the iux produced by Winding W1 and whic passes through the prongs P1 and P2, is similarly change When prongs P1 and P2 are at their extreme outer positions, i. e., when prongs P1 and P2 distance apart, the reluctance of the nia netic path is a maximum. On the other and, when these prongs are at their extreme inner positions, i. e., when these prongs are at their' least distance apart, the reluctance of the magnetic path is a minimum'. Since the winding W2 is in the path of a periodically varyingmagnetic flux, the voltage across the terminals of winding W2 will also vary periodically, this voltage changing from a maximum positive value to a maximum negative value. Accordingly, an alternating current may flow throu h the circuit S which is rangement, it

3 shows another electrically driven deriving alterare the greatest c nating current from the associated continug ously vibrating tuning fork, this arran ment involving a magnetic type. Here the core or cores associated with the generating coil I-are so arranged-as to effectively form a ma Wheatstone bridge, ing placed yin'one of the diagonals of the bridge andthe electrical driving apparatus in the 'other diagonal. Accordingly, the flux Wheatstone bridge o a l etic the generating coil bev connected to the winding W2. In this arproduced b 4the electrical drivin apparatus is prevente from interfering. wit the action of the generating coil.

The magnetic apparatus laced between 5 the prongs P1L and P2 of fork is in the form of a flattened s ool, the bases of which are formed by bars Re and R.V7 and the connecting cross-piece of which is a bar R8, all of these bars being. made of magnetic material. The cross-piece Rs is shown midway between bars R5 and-R7. Ga s J9 and J 10 extend between yprongs P1 and 2, respectively, and bar Re, and gaps Jn and .T12 extend between these prongs, respectively, and bar R7. A windingy a is wound upon the. connecting bar R8, this winding being supplied with energlzlng current from a battery B2 which is connected in series relationship with choke coil L. Choke coil L prevents generated alternating 0 currents from passing through battery B2,

while condenser C prevents the current of battery B2 from flowing through the output circuit S. The apparatus employed herein for maintainin the tuning fork in continuous vibration a r it is started is the same as has been employed in connection with the arrangement of Fig. 1, the same parts being designated by the same reference characters. A portion of the magnetic iiuX derived from winding W1 fiows through bar R6 and another portion of vthis flux flows through bar R7. Assuming that gaps J9 and Ju, adjacent to bar R6 are substantially equal and that gaps J11 and .L2 adjacent to bar R7 are 5 also substantially equal, then more flux may,

erhaps, thread bar R7 than R7. But since ar RB is interposed between the midpoints of bars Re and R7, the ends of bar R8 willbe at substantially equal magnetic potentials so that substantially no vflux produced by winding Wl may flow therethrough. Accordingly, none of the -iux derived from winding W1 will thread bar R and, consequently, no electromotive forces will be established at the'terminals of winding W6 by virtue of the iuX from winding W1. In other words, the action of the winding W8 in the production of electromotive forces will be substantially unaected by the driving mechanism and circuit.

It will be understood that while the terminals of bar R8 are shown in a position midway between the terminals yof bars R6 and R7, respectively, bar R8 need not be so placed, fory it may be `placed in anyposition with respect to bars R6 and R7 so that its terminals are at substantially equal magnetic potentials. Y

As the prongs P1 and P2 of the fork F vi- ?0 brate, gaps J9 and Jlo as well as gaps Jn and Jn will be periodically changed in length so that the reluctance of the magl, netic path followed by the flux arising from the flow of current from battery B2 through 5 choke coil L and through winding W6 will be similarly changed. Accordingly, periodical electromotive forces will be generated by winding W6 and these periodical electromotive forces will result in an alternating` varied organizations without departing from the spirit of the invention and the scope of the appended claims.

What is claimed is: ,y

l. The combination of a tuning fork, means for driving the tuning fork, and means independent of the driving means for generating current always having the natural frequency of vibration of the tuning fork, said means including a coil of wire having an iron core which is midway between and parallel to the prongs of the fork.

2. The-combination of a tuning fork, a solenoid for generating current always of the natural frequency of vibration of said tuning fork, the axis' of the core of said solenoid being parallel to and midway between the prongs of said fork, and means includof the solenoid for driving said fork, said electromagnetic structure and said solenoid being effectively perpendicular to each other and so spaced that said solenoid will be substantially free from the distorting effect of the flux of said electromagnetic structure.

mg an electromagnetic struct-ure independent i 3. In an electrically driven tuning fork arrangement provided with a single generator coil for producing current always having a frequency equal to the natural frequency of vibration of the tuning fork, means for preventing the driving flux from distorting the wave shape of the generated current, said means consisting of an I-shaped soft iron core the stem of which supports the generator coil and lies parallel to the prongs of the tuning fork.

The combination of a tuning fork, electromagnetic means for driving the tuning fork, and means independent of the driving means for generating current always having the natural frequency of vibration of the tunlng fork, said generating means including a coil of wire wound on a core associated with points in the flux paths of the driving means which are at the same magnetic potential with respect to said flux from said driving means.

,5. The combination of a tuning fork, electromagnetic means for driving the tuning the tuning fork, said generating means ini cluding a magnetic system having parallel magnetic paths for the passage of iiux from said driving means and a corefor a generating coil associated with points in said parallel paths which are of the same ma etic potential with respect to .thedriving ux in said paths.

In testimony whereof, I have signed my name to this specification this 13th day of May, 1930.

ANDREW L. MATTE. 

